Method of manufacturing wiring board, and liquid ejection head having wiring board

ABSTRACT

The method of manufacturing a wiring board comprises the steps of: forming a flow channel by covering a groove formed in a resin substrate by means of a covering member; and filling a liquid containing conductive metal into the flow channel, and depositing the conductive metal onto wall faces of the flow channel.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of manufacturing a wiringboard, and a liquid ejection head having the wiring board, and moreparticularly to manufacturing technology for a wiring board in whichplating wires are formed in grooves formed by resin molding.

2. Description of the Related Art

Circuit wiring technology for performing high-density installation hasbeen developed for electronic devices, in order to achieve size andweight reductions, and high functionality, in such devices.

For example, a two-shot molding method and a one-shot molding method areknown for manufacturing circuit components having conductive circuitwires formed on a substrate made of synthetic resin.

In the two-shot molding method, firstly, primary molding is carried outusing a resin containing a plating catalyst, whereupon surfaceroughening (etching) is performed on the primary molding object.Alternatively, the primary molding object is formed of a resin thatcontains no plating catalyst, and surface roughened, then has a platingcatalyst deposited on the roughened surface. Thereupon, secondarymolding is carried out so as to partially cover the primary moldingobject with a resin that contains no plating catalyst. Electrolessplating or electrolytic plating is then carried out on the exposedsurfaces of the primary molding object, thereby depositing metal ontothe circuit forming sections corresponding to the exposed parts of theprimary molding object. In this way, in the two-shot molding method, themolding is carried out twice.

In the one-shot molding method, circuit forming sections are molded in aprescribed shape from synthetic resin, and surface roughening andplating catalyst deposition are then carried out over the whole surfaceof the molding object. Thereupon, electroless plating is performed overthe whole surface of the molding object, the parts other than thecircuit forming sections are masked, and the plating in the areas otherthan the masked areas is removed, whereupon electrolytic plating isperformed on the circuit forming sections, thereby depositing metal onthe circuit forming sections.

However, the two-shot molding method involves a large amount of waste,since it uses the plating catalyst for the whole of the primary moldingobject, and furthermore, the manufacturing process becomes complex,since it requires two molding steps: primary molding and secondarymolding.

The one-shot molding method requires a complicated manufacturingprocess, and also creates wasted material. What is more, if surfaceroughening is carried out by using strongly acidic chemicals, such aschromic acids, in addition to problems relating to environmentalsuitability, there is also a drawback in that if the plating in theregions outside the mask is removed by sandblasting withmicro-particles, or the like, then scratches are liable to occur due tothe scattering of the micro-particles, and non-uniformities arise.

In view of this, Japanese Patent Application Publication No. 2002-270995discloses a method of manufacturing a circuit component in which amolded component is formed by molding synthetic resin into a prescribedexternal shape, preparation processing (surface roughening) is performedby wet blasting on the circuit forming surface of the molded component,a plating catalyst is deposited on the circuit forming surface that hasundergone preparation processing, and the plating catalyst is thenactivated. Subsequently, electroless plating is performed at locationsthat are to form conducting sections, and electrolytic plating is thencarried on the electroless plating sections, thereby forming conductingsections on the circuit forming surface.

Furthermore, Japanese Patent Application Publication No. 2005-50992discloses a wiring board in which non-conductive metal-containing resinlayers containing dispersed metal micro-particles, are formedselectively on a wiring board which is formed by transfer of a visibleimage by an electrophotographic method, whereupon a conductive metallayer is formed on top of the metal-containing resin layer, by means ofelectroless plating and/or electrolytic plating, and a thermally curableresin layer is then formed between the respective metal-containing resinlayers on the substrate.

However, in the method disclosed in Japanese Patent ApplicationPublication No. 2002-270995, desired conducting layers are formed aftersurface roughening by wet blasting and selective catalytic activation(patterning) by UV or heat treatment; however, the selective catalyticactivation by UV irradiation or heat treatment is substantially apatterning step, and hence there is no substantial reduction in thenumber of plating steps. Furthermore, there is also a problem in that itis difficult to carry out patterning by UV irradiation or heattreatment, on the surface of the resin molding that has been formedfreely to a desired shape.

Moreover, the wiring board disclosed in Japanese Patent ApplicationPublication No. 2005-50992 involves the selective formation ofconducting layers by electrophotography. Since the patterning of theconducting layers is carried out by electrophotography, then it isimpossible to achieve a resolution exceeding the resolution of theelectrophotographic process. Furthermore, it is difficult to carry outpatterning by electrophotography on the surface of a resin molding thathas been formed freely to a desired shape.

SUMMARY OF THE INVENTION

The present invention has been contrived in view of the foregoingcircumstances, an object thereof being to provide a method ofmanufacturing a wiring board, and a liquid ejection head comprising thiswiring board, whereby the plating process is shortened, the adhesion ofthe plating is improved, and conducting layers can be formed on asurface having a freely designed shape.

In order to attain the aforementioned object, the present invention isdirected to a method of manufacturing a wiring board, comprising thesteps of: forming a flow channel by covering a groove formed in a resinsubstrate by means of a covering member; and filling a liquid containingconductive metal into the flow channel, and depositing the conductivemetal onto wall faces of the flow channel.

According to the present invention, close adhesion of conductive metalto the flow channel (groove) is improved, and furthermore, themanufacturing process can be simplified.

Preferably, the resin substrate is formed by resin molding by filling aresin material into a mold and curing the resin material.

According to this aspect of the present invention, high-density wiringbecomes possible, and the freedom of the substrate shape and the wiringshape is increased.

Preferably, the liquid containing conductive metal is a material which,when making contact with an electroless plating liquid, induceselectroless precipitation of the metal that is to be deposited; and themethod further comprises the step of forming an electroless platinglayer by using the metal having been deposited on the flow channel as anorigin.

According to this aspect of the present invention, it is possible toreduce the wiring resistance and to form wires which are able to flowhigh current. Furthermore, the material inducing electrolessprecipitation of the metal that is to be plated by making contact withan electroless plating liquid is, for example, an active platingcatalyst material, such as palladium (Pd).

Preferably, the method further comprises the step of forming anelectrolytic plating layer by using the electroless plating layer as aseed layer.

According to this aspect of the present invention, in situationsinvolving a very small signal system and limited wiring area, it ispossible significantly to reduce the steps in the conducting layerformation process by using the wiring process up to the electrolessplating step.

Alternatively, it is also preferable that the liquid containingconductive metal is a conductive paste.

According to this aspect of the present invention, in the case of theconductive paste, the covering member may be left in place, or it may beremoved. If the covering member is left in place, then it forms aprotective layer for the wires, and if the covering member is removed,then connection work becomes easier.

Preferably, the resin substrate is made of an epoxy resin; and themethod further comprises the steps of: introducing an ion exchange groupinto the wall faces of the flow channel by causing liquid containing anoxyacid of sulfur to flow into the flow channel; and then causing aliquid containing copper ions and a reducing agent to make contact withthe groove in the resin substrate.

According to this aspect of the present invention, if the substrateformed with the conducting layer is made of epoxy resin, then in orderto deposit copper ions readily on the substrate, a sulfone group isintroduced into the groove of the substrate. Electroless plating can becarried out readily onto the epoxy resin substrate by depositing asulfone group inside the groove by flowing H₂SO₄ through same.

Preferably, the resin substrate is made of polyimide; and the methodfurther comprises the steps of: introducing an ion exchange group intothe wall faces of the flow channel by causing liquid containing anaqueous alkali solution to flow into the flow channel; and then causinga liquid containing copper ions and a reducing agent to make contactwith the groove in the resin substrate.

According to this aspect of the present invention, if the substrateformed with the conducting layer is made of polyimide resin, then inorder to deposit copper ions readily on the substrate, a cationicexchange group is introduced into the groove of the substrate.Electroless plating can be carried out readily onto the polyimide resinsubstrate by depositing a cationic exchange group inside the groove byflowing KOH through same.

Preferably, the method further comprises the steps of: forming thegroove formed in the resin substrate in a shape whereby a plurality ofdesired conducting layers are connected together; forming the conductinglayers by means of a same operation; and then dividing the conductinglayers by cutting.

According to this aspect of the present invention, it is possible todivide the wires and hence the load in the filling step can be reduced.Moreover, when the groove is formed in a shape whereby a plurality ofconducting layers are connected together, and the connecting section isshaped to form a liquid accumulator, then it is possible to reduce thepressure loss during the step of filling the liquid into the flowchannels, as well as being able to remove bubbles that may arise, bycollecting same in the liquid accumulator.

Preferably, the method further comprises the steps of: forming groovesin both surfaces of the resin substrate; forming a through hole whichconnects the grooves in the surfaces; and forming flow channels bycovering the grooves in the surfaces.

According to this aspect of the present invention, it is possible toform wires on both surfaces of the substrate.

In order to attain the aforementioned object, the present invention isalso directed to a liquid ejection head, comprising: a plurality ofpressure chambers which are connected respectively to a plurality ofnozzles ejecting liquid and are arranged in a two-dimensionalconfiguration; a diaphragm which constitutes wall faces of the pressurechambers on a side of the pressure chambers reverse to a side adjacentto the nozzles; an ejection device structure formed by a plurality ofpiezoelectric elements which respectively deform the pressure chambersand are disposed respectively at positions corresponding to the pressurechambers on a surface of the diaphragm reverse to a surface adjacent tothe pressure chambers; and a substrate on which electrical wires forelectrically connecting a drive circuit for driving the piezoelectricelements with drive electrodes of the piezoelectric elements arearranged, conducting layers to be the electrical wires being formed bythe above-described method.

According to the present invention, it is possible to arrange electricalwires at high density and hence the head can be made more compact insize.

As described above, according to the present invention, close adhesionof conductive metal to the flow channel (groove) is improved, andfurthermore, the manufacturing process can be simplified.

BRIEF DESCRIPTION OF THE DRAWINGS

The nature of this invention, as well as other objects and advantagesthereof, will be explained in the following with reference to theaccompanying drawings, in which like reference characters designate thesame or similar parts throughout the figures and wherein:

FIG. 1A is an oblique diagram of a substrate in which grooves are formedby resin molding according to a first embodiment of the presentinvention, and FIG. 1B is a cross-sectional diagram along line 1B-1B inFIG. 1A;

FIG. 2 is an oblique diagram showing a state where flow channels areformed by covering the grooves by pressing a covering member to thesubstrate formed with the grooves in FIGS. 1A and 1B;

FIG. 3 is a conceptual diagram showing a situation in which the platingcatalyst is filled into the flow channels formed as shown in FIG. 2;

FIGS. 4A and 4B are cross-sectional diagrams showing a state ofcontrolling the roughness of a portion of the grooves of the substrateaccording to a second embodiment;

FIG. 5 is an illustrative diagram showing a molding method using a UVcurable resin according to a third embodiment;

FIGS. 6A and 6B are illustrative diagrams showing a molding method basedon heating and pressurization according to the third embodiment;

FIG. 7A is a plan diagram showing a state in which a recess whichconnects a plurality of grooves is formed in a substrate according to afourth embodiment, and FIG. 7B is a cross-sectional diagram along line7B-7B in FIG. 7A;

FIG. 8 is an illustrative diagram showing a state where the conductinglayer formed on the substrate shown in FIGS. 7A and 7B is to be divided;

FIG. 9 is an illustrative diagram showing conducting layers obtained bydividing the conducting layer along line A-A in FIG. 8;

FIG. 10 is an illustrative diagram showing conducting layers obtained bydividing the conducting layer along lines A-A and B-B in FIG. 8;

FIG. 11 is an illustrative diagram showing a state where platingcatalyst is filled into the grooves formed in the substrate, accordingto a fifth embodiment;

FIG. 12A is a plan diagram showing a substrate having a curved surfaceaccording to a sixth embodiment, and FIG. 12B is a cross-sectionaldiagram along line 12B-12B;

FIGS. 13A and 13B are illustrative diagrams showing states where platingcatalyst is filled into grooves formed in the substrate in FIGS. 12A and12B;

FIGS. 14A and 14B are cross-sectional diagrams showing embodiments ofsubstrates having surfaces other than a flat surface;

FIG. 15A is a plan diagram showing a substrate according to a seventhembodiment, FIG. 15B is a cross-sectional diagram along line 15B-15B inFIG. 15A, and FIG. 15C is a bottom face diagram;

FIG. 16A is an illustrative diagram showing a state where a platingcatalyst is filled into a groove formed in the substrate in FIGS. 15A to15C, and FIG. 16B is a cross-sectional diagram showing a state where aconducting layer is formed on this substrate; and

FIG. 17 is a cross-sectional diagram showing an approximate view of aliquid ejection head according to an eighth embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1A to 3 show a method of manufacturing a wiring board according toa first embodiment of the present invention.

The method of manufacturing a wiring board according to the presentembodiment involves: forming a substrate having grooves by resinmolding, forming flow channels by closing off the grooves after theyhave been formed, introducing a liquid containing a conductive metal(namely, an active plating catalyst material, in other words, a materialwhich induces electroless precipitation of the metal that is to beplated when it makes contact with an electroless plating solution;hereinafter simply referred to as a “plating catalyst”), into the flowchannels, thereby depositing the catalyst onto the grooves, and formingconducting layers which will become electrical wires on the substrate,by means of electroless plating or electrolytic plating.

Firstly, a substrate 10 having grooves 12 is formed by resin molding, asshown in FIG. 1A. Here, for the purpose of the description, the shape ofthe grooves 12 is represented by a simplified shape, but the inventionis not limited in particular to the shape illustrated, and the groovesmay be formed to any desired shape. Furthermore, there are no particularrestrictions on the method of forming grooves by resin molding, providedthat it is a method which enables groove shapes to be formed, such asinjection forming.

FIG. 1B shows a cross-sectional diagram along line 1B-1B in FIG. 1A. Asshown in FIG. 1B, the grooves 12 are formed to a certain depth withrespect to the substrate 10, and will subsequently have electrical wiresformed therein. Furthermore, with regard to the shape of the grooves 12,the groove width is determined by the electrical wiring density, but asregards the depth of the grooves 12, considering that the grooves 12form flow channels along which the liquid containing conductive metal(plating catalyst) travels, and it is hence desirable that the depth isincreased when the density is high, thereby reducing the pressure lossduring travel of the liquid, while at the same time, the adhesion of theconductive layer thus formed can be guaranteed and the electricalresistance of the conducting layer can be reduced, by ensuring thecontact surface area of the conducting layer.

Next, as shown in FIG. 2, a flat plate-shaped covering member (closingmember) 14 is pressed from above against the substrate 10 in which thegrooves 12 have been formed, thereby covering the grooves 12 and formingthe flow channels 16. The covering member 14 of the grooves 12 formingthe flow channels 16 is not limited in particular to any material,provided that it has good adhesion with the substrate 10 in which theconducting layer is to be formed. For example, sheet-shaped siliconerubber, or the like, having low hardness (e.g., in the range of 10 to 30degrees specified in JIS K 6253) has good adhesion characteristics, andis suitable for forming flow channels.

Next, as shown in FIG. 3, in the state where the covering member(closing member) 14 is pressed against the substrate 10, a platingcatalyst tank 18 and a pump 20 are connected to the flow channels 16formed by covering the grooves 12, by means of a tube 22, the pump 20 isdriven, and the liquid (the liquid containing the conductive material,such as the plating catalyst) is circulated through the flow channels16.

As a method of making the liquid containing conductive metal (platingcatalyst) flow into the flow channels 16 (grooves 12), in addition tothis method in which the liquid containing conductive metal is conveyedby creating a pressure differential between the ends of the flowchannels 16, by means of the pump 20, other effective methods are amethod in which the liquid containing conductive metal is made to flowinto the flow channels 16 by capillary action, or a method which isessentially the same as the method of creating a pressure differential,but in which the liquid containing conductive metal is drawn into theflow channels 16 by creating a vacuum therein, or the like.

Next, electroless plating is carried out on the grooves 12 into whichthe plating catalyst has been deposited by introducing the liquidcontaining conductive metal into the flow channels 16, and the coveringmember (closing member) 14 is then removed and electrolytic plating iscarried out, using the electroless plating as a seed layer. In this way,conducting layers are formed in the grooves 12. Thereby, electricalwires are formed in the sections of the grooves 12.

Therefore, it is possible to form wires that have low resistance andalong which high current can flow.

Furthermore, to give a more detailed description of plating in this way,in general, electroless plating is carried out by firstly depositing acatalytic active material (by partial deposition), and then reducing (bypartial reduction) and precipitating the catalytic active material, andperforming electroless plating onto this active material. At the initialstage of depositing the catalytic active material, it is desirable forthe wires to be patterned by using the aforementioned groove wires asthe flow channels 16, since this produces the least waste.

Furthermore, when a general catalytic chemical (catalyst) is introducedinto the flow channels 16 and the catalytic active material is partiallydeposited, then electroless plating should be carried out afterelectrostatic deposition by flowing a tin-palladium (Sn—Pd) colloid andreducing Pd by means of an accelerator. This is because the metal, suchas Cu, Au, Ag, Pt, Pd, or the like, is reduced by a reducing agent, suchas formaldehyde, and hence plating can be formed on this metal.

Furthermore, the characteristics of the aforementioned catalysts aresuch that Pd colloid has a negative charge, which is stabilized by thesuperabundance of Sn²⁺, H⁺ and Cl⁻.

Moreover, it is preferable that only the interior of the grooves 12(flow channels 16) undergoes surface modification. Therefore, an ionexchange group is introduced inside the grooves 12 only, copper ions aredeposited and reduced to metallic copper, and electroless plating isthen carried out using this copper as a catalytic core.

Furthermore, when the material of the substrate 10 is an epoxy resin,then a sulfone group is introduced into the inner surfaces of thegrooves 12, by using H₂SO₄, whereupon copper sulfate is flowed throughthe grooves 12 (flow channels 16), copper ions are deposited and reducedto metallic copper by using NaBH₄, and electroless plating is thencarried out using this copper as a catalytic core. Here, themanufacturing conditions involve flowing a concentrated solution of 14M(mol/liter) for 3 minutes at 60° C., but instead of this, it is alsopossible to flow a low-concentration solution at a higher temperaturefor a longer period of time.

Moreover, when the material of the substrate 10 is polyimide, then theimide chains on the inner surfaces of the grooves 12 are broken by analkaline solution such as KOH, for example, thereby forming a cationicexchange group. Copper ions are deposited and then reduced to metalliccopper by using NaBH₄, and this copper is used as a catalytic core toperform electroless plating. Here, the manufacturing conditions involveflowing a concentrated solution of 5M (mol/liter) for 5 minutes at 50°C., but it is also possible to flow a low-concentration solution at ahigher temperature for a longer period of time.

Furthermore, in the above-described embodiments, a plating catalyst isflowed inside the grooves 12 (flow channels 16), as a liquid containingconductive metal, but instead of this, it is also possible to flow aconductive paste. In this case, the conductive paste injected inside thegrooves 12 forms the electrical wires directly, itself, and hence thereis no need to carry out electroless plating and/or electrolytic plating,and the covering member (closing member) 14 can be left in positionrather than being removed. If the covering member (closing member) 14 isleft in place, then it forms a protective layer for the wires, and ifthe covering member (closing member) 14 is removed, then a beneficialeffect is obtained in that connections can be performed easily.

Next, a second embodiment of the present invention is described.

In this second embodiment, the surface roughness of the inner sides ofthe grooves is controlled to a suitable value in order to improveanchoring effects which enhance the adhesion of the plating to theinterior of the grooves which form the electrical wires. Morespecifically, the surface roughness of the interior of the grooves isset to Ra 0.4 or above in order to improve the adhesion (anchoringeffect) of the plating, and the close contact face with the coveringmember (closing member) which forms the flow channels by covering thegrooves is formed with a surface roughness of Ra 0.2 or below.

In practice, in order to form surface roughness of this kind on theinterior of the grooves of a substrate formed with grooves, and on theclose contact face with the covering member, a surface roughness ispreviously formed in this manner on the mold used for resin molding ofthe substrate, in the portions corresponding to the grooves and theclose contact faces, in such a manner that this surface roughness istransferred to the substrate during resin molding.

As shown in FIG. 4A, the roughness of the smooth surface 24 acorresponding to the close contact face of the groove forming mold 24 isRa 0.2 or less, and the surface roughness of the region indicated by thearrows in FIG. 4A of each of the projecting sections (projections) 24 bcorresponding to the grooves is formed to Ra 0.4 or above. The grooveforming mold 24 can be formed with projecting sections 24 b whichcorrespond to the grooves, by means of micromachining, electroforming,or the like.

When forming the substrate, as shown in FIG. 4B, a thermally curableepoxy resin 28, which has been heated, is filled into the mold 26, thegroove forming mold 24 is then pressed against same from above, and theresin is cured, whereupon the thermally curable epoxy resin 28 isremoved from the mold. Thereby, the portions 28 a of the thermallycurable epoxy resin 28 which correspond to the flat surfaces 24 a of thegroove forming mold 24 are formed to have a roughness of Ra 0.2 orbelow, thus forming a close contact surface with the covering member,and the portions 28 b which correspond to the projecting sections 24 bof the groove forming mold 24 are formed to a surface roughness of Ra0.4 or above.

Next, a third embodiment of the present invention is described.

In this third embodiment, grooves are formed in a substrate by means ofa mold.

There are three types of method for forming the grooves: the grooves maybe molded in a thermally curable epoxy resin, or molded in a resin thatis curable by irradiation of energy, or alternatively, the grooves maybe formed by means of a hot press (heating and pressurization).

Firstly, molding the grooves in a thermally curable epoxy resin is thesame as the method described in FIGS. 4A and 4B. If a thermally curableepoxy resin which has been heated and melted is molded by beingintroduced into a metal mold, then since the thermally curable epoxyresin has good fluidity, it has highly beneficial properties for forminggrooves for high-density wiring.

Next, FIG. 5 shows a molding method using ultraviolet (UV) curableresin. As shown in FIG. 5, the groove forming mold in this case isformed with projection-shaped sections 30 a corresponding to thegrooves, by dry etching, or the like, in an optically transparentmaterial, such as quartz, glass, or the like. An acrylic type UV-curableresin is suitable for use as the resin material. The UV-curable resin 34is introduced into a mold (lower mold) 32, the groove forming mold 30 ispressed against the resin, and UV light is irradiated from above,thereby curing the UV-curable resin 34, and thus forming a substrate inwhich grooves 32 a are formed.

Furthermore, next, FIGS. 6A and 6B show a groove molding method based onheating and pressurization. As shown in FIG. 6A, in this case, a grooveforming mold 36 is heated to the glass transition temperature (Tg point)of a thermoplastic resin 38, and a pressing force is applied to thethermoplastic resin 38, thereby transferring projecting shapes to theresin. Accordingly, as shown in FIG. 6B, grooves 38 a having a shapewhich corresponds to the projecting shape sections 36 a corresponding tothe grooves of the groove forming mold 36.

In this way, by forming a substrate having grooves by means of resinmolding, it is possible to achieve high-density wiring, and furthermore,it is possible to increase the freedom of the shape of the wiring boardand the shape of the wiring.

Next, a fourth embodiment of the present invention is described.

In the present embodiment, recesses in which a plurality of grooves arelinked together are formed on the substrate, the grooves are covered, aplating catalyst is filled into same, and conducting layers are formedand then cut by laser, or the like, to form prescribed conductinglayers.

FIGS. 7A and 7B show a state where a recess having a plurality ofgrooves linked together is formed on the substrate. FIG. 7A is a plandiagram, and FIG. 7B is a cross-sectional diagram along line 7B-7B inFIG. 7A.

As shown in FIG. 7A, two grooves 42 which are substantially parallel areformed respectively in left-hand and right-hand positions, in asubstrate 40, and these four grooves 42 are connected together by meansof a recess 44. Furthermore, as shown in FIG. 7B, in this embodiment,the grooves 42 and the recess 44 formed in the substrate 40 have thesame depth, but the invention is not limited in particular to this.

Then, as shown in FIG. 8, if the conducting layer is cut by laser, orthe like, along line A-A in FIG. 8, for example, then two conductinglayers 42 a and 42 b are obtained as shown in FIG. 9. Furthermore, ifthe conducting layer is cut by laser or the like along both line A-A andline B-B in FIG. 8, then four conducting layers 42 c, 42 d, 42 e and 42f are obtained, as shown in FIG. 10.

Thereby, it is possible to separate the wires and hence the load of theplating catalyst filling step can be reduced.

In this case, the recesses 44 in the connecting sections of theplurality of grooves 42 are formed to a shallow depth, and if therequired portions of the grooves 42 are made deeper, then it is possibleto leave only the portions of the grooves 42 which form the conductinglayers, by grinding the surface and cutting away the connectingsections. In this way, it is also preferable to alter the depth of therecess 44 and the grooves 42.

Next, a fifth embodiment of the present invention is described.

In the present embodiment, liquid accumulating grooves which span acrossa plurality of grooves forming conducting layers are provided in orderto reduce the pressure loss when the liquid (plating catalyst) travelsalong the flow channels formed by covering the grooves formed in thesubstrate. An internal flow channel conveyance pressure is applied tothe grooves and a plating catalyst is thereby deposited in the grooves.

FIG. 11 shows a general overview of this embodiment. As shown in FIG.11, flow channels are formed by placing a covering member (closingmember) 46 in close contact with a substrate 40 formed with grooves 42and a recess 44 shown in FIGS. 7A and 7B, for example, thereby closingoff the grooves 42 and the recess 44. In this case, the recess 44 whichconnects together a plurality of grooves 42 forms a liquid accumulatinggroove which spans across a plurality of grooves 42.

A plating catalyst is sucked in from a plating catalyst tank 48, bymeans of a pump 50, the plating catalyst is injected into the grooves 42(flow channels) from through holes 46 a and 46 c formed in the coveringmember 46, and the plating catalyst is then sucked up from the liquidaccumulating groove (recess 44) via a through hole 46 b and returned tothe plating catalyst tank 48. The plating catalyst is circulated in theflow channels, thereby depositing the plating catalyst inside thegrooves 42.

The grooves 42 formed in the substrate 40 are extremely narrow, as shownin FIGS. 7A and 7B, and hence when it is attempted to flow the liquid(plating catalyst) through same, then the pressure loss is extremelyhigh. It is possible to reduce the pressure loss by using the recess 44as the liquid accumulator which spans across the plurality of grooves42, as in the present embodiment.

Furthermore, if bubbles occur and if these bubbles accumulate in theflow channels when it is sought to flow the liquid (plating catalyst)into the flow channels (grooves 42), then plating will not be depositedin the regions where the bubbles are present, and hence wiringdisconnections will arise. In a case of this kind, by providing a liquidaccumulator, it is possible to collect together the bubbles into theliquid accumulator, and to remove the bubbles. Therefore, disconnectionscan be prevented in the formed electrical wires.

Furthermore, when the liquid (plating catalyst) is circulated throughthe flow channels formed by covering the grooves created in thesubstrate, if the interior of the flow channels is reduced to a vacuumstate and the plating catalyst is then flowed through the flow channelsand filled into same, then the plating catalyst can be introduced anddeposited inside the grooves in a more efficient manner.

Next, a sixth embodiment of the present invention is described.

In the present embodiment, if the substrate surface is curved ratherthan being flat, and has a certain curvature, then the conducting layersare formed following the curvature of the substrate surface.

FIGS. 12A and 12B show a substrate in the present embodiment. FIG. 12Ais a plan diagram, and FIG. 12B is a cross-sectional diagram along line12B-12B in FIG. 12A. As shown in FIG. 12A, the planar shape of thesubstrate 52 in the present embodiment is similar to that in FIG. 7A,and a plurality of grooves 54 are formed extending in four directionsfrom a recess 56 provided in the central portion of the substrate 52.

However, in the present embodiment, as shown in FIG. 12B, the surface ofthe substrate 52 on which the grooves 54 and the recess 56 are formedhas a curved shape which projects in the upward direction.

FIGS. 13A and 13B show a situation where a plating catalyst is filledinto the substrate 52 in the present embodiment.

For example, as shown in FIG. 13A, the surface of the covering member 58having a curvature matching the curvature of the surface of thesubstrate 52 is placed in close contact with the substrate 52, a platingcatalyst is sucked in from a plating catalyst tank 60 by means of a pump62, and the plating catalyst is filled into the flow channels (grooves54) from the through holes 58 a and 58 c formed in the covering member58. The plating catalyst which has flowed into the flow channels returnsto the plating catalyst tank 60 via a through hole 58 b in the coveringmember 58, from the central recess 56. In this way, by driving the pump62, the plating catalyst is circulated and plating catalyst is depositedinside the flow channels (grooves 54).

Furthermore, as shown in FIG. 13B, it is also possible to reverse thedirection of circulation of the plating catalyst, and to introduce theplating catalyst into the recess 56 from the central through hole 58 b,in such a manner that it flows from the recess 56 into the peripheralflow channels (grooves 54).

In this way, according to the present embodiment, even if the substratesurface is curved, rather than flat, it is still possible to formconducting layers on this surface.

Moreover, as shown in FIG. 14A, flow channels 65 are formed by placing acovering member 66 which follows the curved shape of a substrate 64, inclose contact with a curved substrate 64 having a surface with anarbitrary curvature, and by introducing a metal catalyst 68 into theflow channels 65, it is possible to form conducting layers having thearbitrary curvature.

Furthermore, as shown in FIG. 14B, flow channels 65 are formed byplacing a covering member 66 matching the shape of step-shaped flowchannels 65, in close contact with step-shaped flow channels 65 whichcombine perpendicularly arranged flat surfaces. By introducing theplating catalyst 68 into the flow channels 65, it is possible to formconducting layers which bend in the stepped shape.

Next, a seventh embodiment of the present invention is described.

In the present embodiment, grooves are formed on both surfaces of thesubstrate, through holes which connect the grooves on both surfaces areformed in the substrate, and conducting layers are formed on bothsurfaces of the substrate.

FIGS. 15A, 15B and 15C show a substrate according to the presentembodiment. FIG. 15A is a plan diagram, and FIG. 15B is across-sectional diagram along line 15B-15B in FIG. 15A, and FIG. 15C isa bottom face diagram.

As shown in FIG. 15A, the planar shape of the substrate 70 of thepresent embodiment is similar to that of FIG. 7A, having a plurality ofgrooves 72 formed extending in four directions from a recess 74 providedin the central portion of the substrate 52. In the substrate 70 of thepresent embodiment, a through hole 76 is formed in the center of therecess 74.

Furthermore, as shown by the cross-sectional diagram in FIG. 15B, thesubstrate 70 according to the present embodiment also has a groove 78formed in the rear surface thereof, and the two grooves 72 and 78 areconnected together by means of the through hole 76. As shown by thebottom face diagram in FIG. 15C, the groove 78 in the rear surface isformed so as to extend in one direction from the through hole 76.

FIG. 16A shows a state where plating catalyst is filled into the grooves72 (flow channels) in the substrate 70 of this kind. In the substrate 70according to the present embodiment, the grooves 72 and 78 are formed onboth surfaces of the substrate 70, and covering members 80 and 82 areplaced respectively in close contact the surfaces of the substrate 70.The covering member 80 placed in close contact with the front surface ofthe substrate 70 has through holes 80 a and 80 b connected to the groove72 in the surface of the substrate 70, and the covering member 82 placedin close contact with the rear surface of the substrate 70 has a throughhole 82 a connected to the groove 78 in the rear surface of thesubstrate 70.

A pump 86 is connected to a plating catalyst tank 84, the pump 86 isdriven, plating catalyst is sucked up from the plating catalyst tank 84,and the plating catalyst flows into the groove 72 in the surface of thesubstrate 70 from the through holes 80 a and 80 b of the covering member80 on the surface of the substrate 70. The plating catalyst injectedinto the groove 72 flows from the groove 72 into the recess 74, flowsfrom the through hole 76 in the center of the substrate 70 into thegroove 78 in the rear surface of the substrate 70, and then flows outfrom the through hole 82 a of the covering member 82 placed in closecontact with the rear surface side of the substrate 70, in such a mannerthat it returns to the plating catalyst tank 84.

Thereby, the plating catalyst is circulated through the grooves 72 and78 in both the front surface side and the rear surface side of thesubstrate 70, and hence the plating catalyst can be deposited in both ofthe grooves 72 and 78.

Accordingly, as shown in FIG. 16B, it is possible to form conductinglayers 88 respectively on both surfaces of the substrate 70. In thisway, according to the present embodiment, it is easy to form wires onboth surfaces of the substrate.

Next, an eighth embodiment of the present invention is described.

In the present embodiment, when an integrated wiring board is formed tohave ejection devices which eject liquid and conducting layers which areelectrically connected to the drive elements of the ejection devices anda switching IC, then the conducting layers are formed by means of theabove-described method of forming conducting layers (method ofmanufacturing a wiring board) according to the present invention.

FIG. 17 is a cross-sectional diagram showing an approximate view of aliquid ejection head according to the present embodiment in whichejection devices and a wiring board having conducting layers are formedin an integrated fashion.

The liquid ejection head 150 shown in FIG. 17 is constituted by bondingtogether a nozzle plate 160, a cavity plate 162, a diaphragm 156 havingpiezoelectric elements 158 formed thereon, an intermediate plate 170 andan ink pool member 164.

Nozzles 151 for ejecting ink droplets are formed in the nozzle plate160. Hole sections 162 a corresponding to pressure chambers 152, andgroove sections 162 b which constitute portions of ink supply channels153 described hereinafter, are formed in the cavity plate 162. One sideof each hole section 162 a (the lower side in FIG. 17) is covered by thenozzle plate 160, and the other side (the upper side in FIG. 17) iscovered by the diaphragm 156, and hence the pressure chamber 152 isformed thereby.

The ink pool member 164 has a vessel-shaped structure formed so as to beopen on one side, and the ink pool member 164 is bonded onto theintermediate plate 170 in such a manner that the open side thereof isorientated toward the lower side in FIG. 17. The space formed by the inkpool member 164 and the intermediate plate 170 is an ink pool (commonliquid chamber) 155, which is composed so as to cover a regioncorresponding to the plurality of pressure chambers 152. The holesections 170 a and 156 a, and the groove sections 162 b, whichconstitute a portion of the ink supply channels 153 providedrespectively for the pressure chambers 152, are formed respectively inthe intermediate plate 170, the diaphragm 156 and the cavity plate 162.The ink pool 155 and the pressure chambers 152 are connected via the inksupply channels 153 constituted by these members (170 a, 156 a and 162b). Ink supplied from an ink tank (not illustrated) is accumulated inthe ink pool 155, and is distributed and supplied from the ink pool 155to the respective pressure chambers 152, via the ink supply channels153.

The piezoelectric elements 158, each of which has an individualelectrode (drive electrode) 157 on the upper surface thereof, areprovided at positions corresponding to the pressure chambers 152, on thesurface of the diaphragm 156 reverse to the side adjacent to thepressure chambers 152 (in other words, on the ink pool 155 side). Thediaphragm 156 is made of a conducting member, such as stainless steel,and also serves as a common electrode for the plurality of piezoelectricelements 158. It is also possible to form a common electrode on thesurface of the diaphragm 156.

Recess sections 170 b corresponding to the piezoelectric elements 158are formed in the intermediate plate 170. Thereby, a prescribed space isguaranteed in the peripheral region of each piezoelectric element 158,and therefore it is possible to achieve the print head 150 having goodejection characteristics, without impeding the displacement of thepiezoelectric elements 158.

The intermediate plate (wiring board) 170 is composed so as to bebroader than the diaphragm 156 or the ink pool member 164. A drivecircuit 172 constituted by a switch IC, for example, is provided on thefront surface side (ink pool 155 side) of an extension section 170 c (ofthe intermediate plate 170) which projects from the side face of thehead.

Electrical wires (internal wires) 174 which are patterned in aprescribed shape are provided on the intermediate plate 170. In theembodiment shown in FIG. 17, each electrical wire 174 is constituted bya horizontal section 174 a formed horizontally along the front surfaceside (ink pool 155 side) of the intermediate plate 170, from theposition where the drive circuit 172 is disposed, and a vertical section174 b which passes vertically through the intermediate plate 170 fromone end of the horizontal section 174 a. One end of the electrical wire174 is connected electrically to the drive circuit 172, and the otherend thereof is connected electrically to the individual electrode 157 ofthe piezoelectric element 158 via an electrical connecting section 176.An insulating and protective film (not shown) made of resin, or thelike, is formed on the portion of the surface of the intermediate plate170 which makes contact with the ink inside the ink pool 155.

In the present embodiment, in the liquid ejection head 150 having thecomposition described above, an ejection device structure whichprincipally comprises the nozzle plate 160, the cavity plate 162, andthe diaphragm 156 having the piezoelectric elements 158 formed thereon,is unified with the intermediate plate 170 which forms the substrateincluding conducting layers that provide electrical connections betweenthe piezoelectric elements 158 and the switching IC, and theseconducting layers are formed by means of the conducting layer formingmethod such as that described in the respective embodiments mentionedabove. Accordingly, it is readily possible to achieve high-densityarrangement of electrical wires.

It should be understood, however, that there is no intention to limitthe invention to the specific forms disclosed, but on the contrary, theinvention is to cover all modifications, alternate constructions andequivalents falling within the spirit and scope of the invention asexpressed in the appended claims.

1. A method of manufacturing a wiring board, comprising the steps of:forming a flow channel by covering a groove formed in a resin substrateby means of a covering member; and filling a liquid containingconductive metal into the flow channel, and depositing the conductivemetal onto wall faces of the flow channel.
 2. The method as defined inclaim 1, wherein the resin substrate is formed by resin molding byfilling a resin material into a mold and curing the resin material. 3.The method as defined in claim 1, wherein: the liquid containingconductive metal is a material which, when making contact with anelectroless plating liquid, induces electroless precipitation of themetal that is to be deposited; and the method further comprises the stepof forming an electroless plating layer by using the metal having beendeposited on the flow channel as an origin.
 4. The method as defined inclaim 3, further comprising the step of forming an electrolytic platinglayer by using the electroless plating layer as a seed layer.
 5. Themethod as defined in claim 1, wherein the liquid containing conductivemetal is a conductive paste.
 6. The method as defined in claim 1,wherein: the resin substrate is made of an epoxy resin; and the methodfurther comprises the steps of: introducing an ion exchange group intothe wall faces of the flow channel by causing liquid containing anoxyacid of sulfur to flow into the flow channel; and then causing aliquid containing copper ions and a reducing agent to make contact withthe groove in the resin substrate.
 7. The method as defined in claim 1,wherein: the resin substrate is made of polyimide resin; and the methodfurther comprises the steps of: introducing an ion exchange group intothe wall faces of the flow channel by causing liquid containing anaqueous alkali solution to flow into the flow channel; and then causinga liquid containing copper ions and a reducing agent to make contactwith the groove in the resin substrate.
 8. The method as defined inclaim 1, further comprising the steps of: forming the groove formed inthe resin substrate in a shape whereby a plurality of desired conductinglayers are connected together; forming the conducting layers by means ofa same operation; and then dividing the conducting layers by cutting. 9.The method as defined in claim 1, further comprising the steps of:forming grooves in both surfaces of the resin substrate; forming athrough hole which connects the grooves in the surfaces; and formingflow channels by covering the grooves in the surfaces.
 10. A liquidejection head, comprising: a plurality of pressure chambers which areconnected respectively to a plurality of nozzles ejecting liquid and arearranged in a two-dimensional configuration; a diaphragm whichconstitutes wall faces of the pressure chambers on a side of thepressure chambers reverse to a side adjacent to the nozzles; an ejectiondevice structure formed by a plurality of piezoelectric elements whichrespectively deform the pressure chambers and are disposed respectivelyat positions corresponding to the pressure chambers on a surface of thediaphragm reverse to a surface adjacent to the pressure chambers; and asubstrate on which electrical wires for electrically connecting a drivecircuit for driving the piezoelectric elements with drive electrodes ofthe piezoelectric elements are arranged, conducting layers to be theelectrical wires being formed by the method as defined in claim 1.